I. Field of the Invention
This invention relates generally to electrosurgical instruments, and more particularly to an improved, bipolar, hook-probe for use in endoscopic surgery to provide enhanced cutting and coagulation capability over existing hook-probe instruments.
II. Discussion of the Prior Art
In the course of minimally invasive procedures, electrosurgery is often employed to effect cutting and coagulation or cauterization of tissue structures. The electrosurgical instruments employed have one or more electrodes adapted to be energized by RF currents. In so-called monopolar systems, the current passes from the instrument, through the tissue to be cut or coagulated to a body plate type return electrode located remote from the surgical site. Since the electrical currents tend to follow a path of least resistance from the instrument to the return electrode, the path is somewhat unpredictable and it has led to burns at unintended locations.
In the case of bipolar instruments, the active electrode and the associated return electrode are disposed in close proximity to one another on the instrument itself so that there is less likelihood of current flow to tissues other than intended tissue structures being operated upon. Bipolar electrosurgery is considered by most as a safer procedure.
In the Fleenor et al. U.S. Pat. No. 5,484,435, there is described a bipolar electrosurgical instrument intended for use in minimally invasive surgical procedures for both cutting and coagulating tissue, thus obviating the need for an instrument exchange where separate instruments as required for the cutting and coagulating functions. The instrument described in the ""435 patent comprises a handle 98 disposed at one end of an elongated tubular barrel 96 having as one electrode a hook 90 in the form of a bent uninsulated wire and a one-piece return electrode 92 that is somewhat hemispherical in shape that projects outwardly from the distal end of the barrel and which has a slot formed therein for receiving the hook electrode therethrough. The walls of the slot are insulated so as to prevent short-circuiting with the hook member electrode but the portions of the electrode 92 on both sides of the slot are not insulated from each other. A lever assembly 98 on the handle, which when manipulated, allows the active hook electrode 90 to be extended and retracted relative to the fixed return electrode 92. In use, the active hook electrode is made to frictionally engage or slightly puncture target tissue to grip it. Then, by manipulating the lever 98 on the handle, the tissue can be drawn proximally to engage the return electrode. The electrosurgical generator is then activated to achieve cutting or coagulation.
The device of the ""435 patent achieves acceptable levels of cutting because of the high current density present due to the small size and shape of the active electrode. However, coagulation with that instrument leaves much to be desired, given the small electrode surface area of the active electrode compared to that of the one-piece return electrode 92.
Bipolar coagulation devices require equal electrode surface area or a ratio of 1:1 for optimum results. Bipolar cut devices require a 4:1 or greater return electrode to active electrode ratio for effective precision cutting. Prior art bipolar devices have tended to be either good coagulators or good cutters, but not both.
The present invention is deemed to be a substantial improvement over the prior art as represented by the Fleenor et al. ""435 patent. The device constructed in accordance with the present invention provides a hook probe that not only effectively cuts target tissue, but it also provides superior coagulation.
The Rydell U.S. Pat. No. 5,282,799 in the embodiment illustrated in FIG. 9 discloses an arrangement in which a pair of loop electrodes 28 and 30 are mounted on the distal end of a reciprocally movable control rod 60 that can be shifted longitudinally, via a thumb slide 224 so as to be extended from the distal tip of the instrument or retracted fully within the distal tip of the instrument. Also present on the insulating distal tip member 70 of the instrument are electrode surfaces 71 and 73. A push-button 216 moves longitudinally with the control rod so as to overlay a first dome switch 210 or a second dome switch 212. When the loop electrodes 28 and 30 are in their distalmost position projecting from the distal end of the instrument, the push-button 216 overlays the dome switch 210. Thus, when the push-button 216 is depressed, a cutting potential is applied between the electrodes 28 and 30. When the loop electrodes 28 and 30 are retracted by shifting the thumb slot in the proximal direction, the push-button 216 overlays the dome switch 212 so when it is depressed, a coagulating voltage is applied to the electrodes. Since the loop electrodes are retracted into a recess in the distal tip, they are not exposed to tissue. Only tissue bridging the surface contacts 71 and 73 will have a coagulating current flowing through it.
In this design, when electrosurgical cutting is involved, the same cutting voltage that is applied to the loop electrodes 28 and 30 is also present between the surface-mounted coagulating electrodes 71 and 73. The surgeon must, therefore, exercise increased caution to avoid inadvertent contact of non-target tissue with the surface electrodes as the cutting operation is taken place.
The Rydell U.S. Pat. No. 5,891,141 describes an electrosurgical instrument for cutting and coagulating tubular tissue structures, such as vein and arterial tissue, by grasping the tissue between a pair of spaced-apart electrodes that when energized by RF energy coagulates the portion of the tissue structure contained between the two electrodes. Once desiccated, a thumb switch is manipulated to cause a cutting blade to mechanically cut through the desiccated tissue.
The Roos U.S. Pat. No. 5,269,780 describes an electrosurgical instrument designed to both cut and coagulate tissue. It includes a handle having a pair of stationary L-shaped hook electrodes 22 and 23 projecting from a distal end of the handle in parallel, spaced-apart relation. These electrodes function to coagulate tissue and once coagulated, a cutting electrode 21 is made to descend into the gap between the two stationary electrodes while a cutting voltage is applied between it and the two stationary coagulating electrodes which function as a neutral. No provision is made for retracting any of electrodes 21-23 into the handle member.
The foregoing objects and advantages of the present invention are provided by designing a bipolar electrosurgical cutting and coagulating probe that has an elongated, tubular barrel with a proximal end, a distal end and a lumen extending between the two. A handle member is affixed to the proximal end of the barrel and an end effector is affixed to its distal end. The end effector in accordance with the present invention includes first and second electrodes that are placed in parallel, closely-spaced, non-contacting relationship where each is of a relatively large surface area. A conductive, reciprocally movable hook member is operatively coupled to a mechanism on the handle member so that manipulation of the mechanism causes the hook member to be movable in and out of the space separating the first and second electrodes from one another. The hook member has a relatively small surface area compared to the combined surface area of the first and second electrodes. A plurality of elongated conductors extends through the handle and into the lumen of the barrel, the first being electrically connected to the first electrode, the second to the second electrode and the third to the hook member electrode. In its cut mode, an appropriate RF voltage is applied between the hook electrode and the first and second electrodes as tissue comes into contact with all three electrodes or is gripped by the hook drawn toward and against the first and second electrodes which together function as the return electrode for the bipolar instrument. When operating in a coagulation mode, however, the RF voltage is only applied between the first and second electrodes. The hook is not energized. Because the first and second electrodes are of generally equal surface area, coagulation occurs over the entire active surfaces of the first and second electrodes, providing appreciably greater margins than result from the Fleenor-type instrument,
There are, of course, additional features of the invention that will be described hereinafter which will form the subject matter of the appended claims. Those skilled in the art will appreciate that the preferred embodiments may readily be used as a basis for designing other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions since they do not depart from the spirit and scope of the present invention. The foregoing and other features and other advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.